1. Field of the Invention
The present invention relates to control of pumps. More particularly, the present invention relates to control of pumps by monitoring pump stroke for determining optimum stroke cycles.
2. Description of the Prior Art
Electro-mechanical apparatus for monitoring the operation of sucker rod type well pumping units is known to those skilled in the art as evidenced by my previous U.S. Pat. Nos.: 3,851,995; 4,363,605; 4,043,191; 4,208,665 and 4,873,635.
U.S. Pat. No. 3,817,094 to Montgomery weighs the deflection of the walking beam of a pumpjack unit for providing a signal used for controlling the motor of a pumpjack unit.
U.S. Pat. No. 3,838,597 to Montgomery measures the load during the pumping action and produces a signal which shuts-in the well upon encountering a pump-off condition.
U.S. Pat. No. 4,490,094 to Gibbs measures the instantaneous motor speeds of revolutions for a pumpjack unit, and compares the results with the instantaneous speeds of revolutions of a pump-off condition in order to shut-in a pumpjack unit.
In my U.S. Pat. No. 4,873,635 there is provided a pump-off control (poc) for a pumpjack unit that indirectly measures the efficiency of the pumping action by counting the length of time required for the pumpjack unit to make one complete cycle of operation, or at least a portion of the downstroke. When the measured time interval changes a predetermined amount, the well is shut-in for a predetermined length of time. The portion of the measured pumping cycle must include that part of the downstroke where fluid pounding historically occurs. That disclosure is hereby incorporated by reference.